restart and standby

The motherboard is ASUS P4B533 (probably a special batch for the manufacturer).The OS is Windows xp Professional (2003 vintage with no updates).I have replaced the original RAM with 2 x 512MB, 184 pin DIMM modules.I have replaced the original hard drive with a SAMSUNG 200GB/7200rpm/8M/PATA drive (for security reasons as I am passing the computer on to a friend).I have also installed an additional fan and replaced the original CD and floppy drives and replaced the ribbon cables with round ones.All is up and ready to go except that whereas on manual boot up there is no problem, when restart icon is selected, the computer restarts and goes as far as the screen identifying motherboard and drives; but shows an error message "hardware error detected- pres F1 to continue DEL to enter SETUP 03/14/2003 - 1845G/ICH4 -P4B533 - VM".When F1 is pressed boot up continues as normal.How can I identify the hardware error and correct it.There is a second problem - on shut down the standby icon does not display.Neither of these problems existed when the computer was new and may have arisen when RAM was increased.